TKOPerformance wrote:

Does the dimmer function on the headlight switch?

Generally it functions yes! i can "dim" it all the way down and turn off courtesy lights.. before this happened it used to work .. if that helps

rpm wrote:

Ever time my instrument lights failed to work, it turned out to be a ground issue.

Where or which ground did you have an issue with?

Not 100% sure about the '65 clusters, but in my '67 the dash lights ground to the metal backing plate of the cluster, which is in turn grounded.

But are you saying the dimmer now doesn't work?

When a light doesn't work there's only three possible causes.  The bulb is bad (unlikely that all your bulbs are bad at the exact same time), not getting power, or not getting ground.  Its possible the ground to the backing plate, if so equipped, failed and that's your issue.  Its also possible something in the headlight switch, which feeds the lighting circuit, failed.

I would pull the cluster and test one of the sockets to see which you are not getting (ground or power).

I had a similar problem on my '66. The cluster lights were initially dim and finally went totally out. After restoring my cluster with new lamps and 5v regulator, I ensured that the grounds were good but the problem persisted. I ultimately found dead spots in the dimmer function on the switch. Without removing it, I sprayed it with electrical contact cleaner and repeatedly rotated the knob back and forth to clean the contact. Problem solved!

I didn't mean to imply that the regulator was part of the lighting circuit. It was just one of the electrical components that required replacement in the restoration. Sorry for the confusion!